The present invention relates generally to vehicle wheels. More particularly, it is concerned with wheels for trucks and other utility vehicles and wear resistant coatings and methods for applying said coatings.
Vehicle wheels can experience a degree of wear deleterious to their immediate and long-term function due to their extended and rigorous use during and through the operation of motor vehicles. One mechanism by which said wear occurs is the extended frictional contact between the tire mounted on the wheel and the wheel itself. This occurs due to sliding between the tire and wheel, creating consequent abrasion, adhesion, and other wear issues. This problem is particularly acute when dealing with large trucks and other utility vehicles. It is further exacerbated where wheels are used on and with military vehicles, where the degree of wear and tear experienced due to operation for extended periods in harsh conditions can lead to premature wheel wear and/or failure.
Possible solutions for the aforesaid problem include the use of stronger more durable materials in forming wheels, and providing wear resistant coatings between wheels and tires. Providing wheels formed from steel is one obvious approach to the problem of creating more durable wheels. However, though steel wheels are inherently more wear resistant, they have been largely replaced by aluminum wheels due to the lighter weight of the latter. (Steel has 2.8 times the density of aluminum). Anodizing can be used to make aluminum itself more wear resistant. Unfortunately, some types of anodizing can reduce fatigue strength of the metal by up to 50%. Application of wear resistant metallic or ceramic coating has also been tried. (See, e.g., U.S. Pat. No. 6,872,425). However, prior art coating materials/methods, such as those described in the '425 patent, are expensive, complex, and may include or require pre-coating preparation such as mechanical roughening, knurling and/or abrasive grit blasting. Thus, a definite need exists for further advances in the field of wear resistant wheel coatings and methods capable of protecting vehicle wheels from wear and corrosion, particularly from such wear and corrosion as arises from wheel/tire frictional contact, and even more particularly from such wear and corrosion in truck, utility and military vehicle wheels formed from aluminum.
This need is met in a novel and non-obvious way by the method and coating of the invention, which in its most basic embodiments, involves the addition of a slip agent to an appropriate wheel coating. In its more preferred embodiments, the slip agent is one that will not adversely impact intercoat adhesion in a multi-coat wheel coating system. And, in its most preferred embodiment, as discussed in detail herein, the slip agent is included in an intermediate coating applied between a wheel's primer and topcoat. More particularly, the intermediate coating is comprised of a MIL-P-53022 Type I or Type II lead and chromate free, corrosion inhibiting epoxy primer with an addition of 3% polytetrafluoroethylene (PTFE), and is preferably applied to the wheel intermediate the primer and topcoat in accordance with the chemical agent resistant coating (CARC) system used on tactical military equipment.